Android-ObservableScrollView is a library that provides scrollable widgets for Android with scrolling and touch event handling. It enables developers to create flexible and interactive UI components that respond to scroll events, such as parallax effects, sticky headers, and more.

Pros

• Easy integration with existing Android projects
• Supports various scroll view types (e.g., ListView, RecyclerView, ScrollView)
• Customizable scroll behavior and animations
• Extensive documentation and sample code available

Cons

• May introduce additional complexity for simple scroll implementations
• Performance impact on older devices with complex scroll effects
• Limited support for nested scrolling scenarios
• Requires careful implementation to avoid conflicts with native Android scrolling

Code Examples

1. Creating an ObservableScrollView:

ObservableScrollView scrollView = findViewById(R.id.scroll);
scrollView.setScrollViewCallbacks(this);

2. Implementing scroll callbacks:

@Override
public void onScrollChanged(int scrollY, boolean firstScroll, boolean dragging) {
    // Handle scroll changes
}

@Override
public void onDownMotionEvent() {
    // Handle down motion event
}

@Override
public void onUpOrCancelMotionEvent(ScrollState scrollState) {
    // Handle up or cancel motion event
}

3. Creating a parallax effect:

@Override
public void onScrollChanged(int scrollY, boolean firstScroll, boolean dragging) {
    float alpha = Math.min(1, (float) scrollY / getActionBarSize());
    toolbar.setBackgroundColor(ScrollUtils.getColorWithAlpha(alpha, baseColor));
    ViewHelper.setTranslationY(image, scrollY / 2);
}

Getting Started

1. Add the dependency to your build.gradle file:

dependencies {
    implementation 'com.github.ksoichiro:android-observablescrollview:1.6.0'
}

2. Add an ObservableScrollView to your layout:

<com.github.ksoichiro.android.observablescrollview.ObservableScrollView
    android:id="@+id/scroll"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <!-- Your content here -->
</com.github.ksoichiro.android.observablescrollview.ObservableScrollView>

3. Implement the ScrollViewCallbacks interface in your Activity or Fragment:

public class MainActivity extends AppCompatActivity implements ObservableScrollViewCallbacks {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        ObservableScrollView scrollView = findViewById(R.id.scroll);
        scrollView.setScrollViewCallbacks(this);
    }

    // Implement callback methods
}